/Engine/Source/Developer/SourceControl/Public/ISourceControlModule.h
Delegate called once the user has confirmed that they want to submit files to source control BUT before the files are actually submitted. It is intended for last minute checks that can only run once there is no chance of the user canceling the actual submit. At this point the only way to prevent the files from being submitted is for this delegate to return errors.
typedef TMulticastDelegate_ThreeParams< void, const [TArray](API\Runtime\Core\Containers\TArray)< [FString](API\Runtime\Core\Containers\FString) > &, [TArray](API\Runtime\Core\Containers\TArray)< [FText](API\Runtime\Core\Internationalization\FText) > &, [TArray](API\Runtime\Core\Containers\TArray)< [FText](API\Runtime\Core\Internationalization\FText) > & > FSourceControlPreSubmitFinalizeDelegate